There are a variety of food, beverage and healthcare products for which a non-removable closure would be advantageous. A non-removable closure system is generally understood to be one in which, following attachment of the closure to the container body, the closure cannot be detached from the container without deliberately applying such large forces that would at least partially damage the container and/or the closure. Such damage would thus prevent continued use of the container body and/or closure.
For example, it is well known to provide an injection molded preform with a relatively thick finish area having an external thread, and a lower body portion that is subsequently blow molded to form a relatively thin container body. The relatively thick finish wall provides the necessary structural strength for secure application of a closure having a complementary internal threaded portion, while the expanded container body is sufficiently strong to withstand product filling, handling and expected use, but is often substantially weaker than the finish area. The preform(s)/container(s) for such applications are typically made from thermoplastic polymers such as polyesters (e.g., polyethylene terephthalate PET) and polyolefins (e.g., polypropylene or polyethylene). The closure is also typically a molded plastic article, formed separately from the container, and may be made of polyolefin or polyester.
Most applications for such thermoplastic containers and closures are single use applications, wherein the container and closure are essentially discarded after the product is used. In such applications, it is desirable to minimize the amount of material required, and minimize the complexity of the injection and blow molding equipment, in order to produce the container and closure at a competitive price. These limitations on material usage and equipment/process complexity are also constraints on the design of a non-removable closure/container system where it is desired that customer be unable to remove the closure and refill (reuse) the container. However, these constraints make it more difficult to design a closure/container system with sufficient structural integrity to withstand (resist) customer attempts to remove the closure.